A RAW Processing Primer

[yelvertoft]

Ok, you’ve got your dSLR or pro-sumer camera, you’ve been playing around with it for a while and are getting pretty confident. You keep hearing people on the forums making bold statements like “Raw capture is the only way to use your camera, you cannot call yourself a serious photographer unless you use raw.”

So how much of this is true? It depends very much on what kind of photography you like to do and more importantly, how you like to view and use the resulting images. Let’s begin by outlining some benefits and disadvantages of using raw capture mode. There’s more to it than I’ve outlined below but lets just stick to the basics with this article.

The Advantages:
· You can correct a variety of errors, such as setting the incorrect white balance or exposure compensation, that you may have made at the time you took the picture. The scope and extent of correction is greater than you could get away with by post-processing in JPEG.
· The fine detail captured in the image is preserved with the maximum possible clarity.

The Disadvantages:
· Raw capture takes up a lot more space on the memory card, you can’t take as many pictures before the card is full.
· Raw images require processing before they can be viewed or printed by “standard” applications. This takes time and effort.

What is raw capture?
Raw is not an acronym (for once), raw means unprocessed. The sensor captures the image data and files it away without the camera using any of the settings normally applied during JPEG processing such as white balance adjustment, contrast adjustment, saturation adjustment, etc. What light hit the sensor is filed away “as is”.

So when should you use raw mode?
· If you are demand the very highest level of detail in your images, you may be doing fairly severe image crops that require this level of detail.
· If you are a professional or wish to regularly sell your images as a bit of extra cash. If this is the case you probably don’t need to read this article anyway.
· If you wish to print your images at bigger sizes than A4 (roughly 12”x8”).

When isn’t it so important to use raw mode?
· If you are taking ‘snapshots’, pictures that you have just grabbed for yourself, a quick snap of a moment in time.
· If you only intend viewing your pictures on a small/medium sized monitor.
· If you don’t intend to print your images any bigger than A4.

Having got a load of pictures in raw mode, what do you do now? You need to process them before they can be viewed or printed using standard applications. I will try and explain the basics of this processing using Adobe Camera Raw (henceforth referred to as ACR). This is a free plug-in that works with Photoshop Elements 3 or 4, or Photoshop 7.0/CS/CS2 for that matter if you have it (though not all versions of ACR are compatible with 7.0 or CS). Another popular free application for raw processing is Raw Shooter Essentials. If it is capable of raw capture then your camera will have come bundled with a piece of software to enable you to process the raw files. The basics I am trying to explain below will hopefully be similar to the options available in your processing package.

On loading your raw image file into ACR, you will be presented with a screen showing the image on the left and a histogram with a bunch of sliders and pull-downs for adjustment on the right. The histogram shows the darkest and brightest points in an image. The horizontal axis represents the brightness and the vertical axis represents the number of pixels present in the image at that particular brightness. The histogram should be watched closely during all the adjustments to see what is happening to the picture as you edit.

To begin, adjust the White Balance
There is a pull-down box available which will hopefully list the presets available in your camera’s menu. If the version of ACR you are using does not support the camera you are using this may not be the case. You can select from the pull down list, the setting that matches the lighting conditions the picture was taken in. This is a good starting point. You can make further adjustments to the white balance settings, if required, using the two sliders available. These are labelled Temperature and Tint. The temperature slider controls the yellow/blue balance of the picture making the image look warmer or cooler, the tint slider controls the magenta/green balance and is useful for fine tuning. You can make quite dramatic changes to the overall feel and atmosphere of the picture by simply changing these two sliders.

Next stage, Exposure, Shadows, Brightness, and Contrast.
The Exposure, Shadows, Brightness, and Contrast controls let you shape the overall tonality of the image.
The exposure control sets the white point in the image.
The shadows control sets the black point in the image.
The brightness control adjusts the midtone in the image and the contrast increases contrast around the midtone set by brightness. That sounds a lot more complicated than it really is. The best thing you can do is play with an image yourself and see what the effects are. Keep a careful eye on the histogram whilst tweaking, it’ll teach you a lot about what’s happening to the image. Whilst using the exposure and shadows sliders, ACR allows you to view the extent of “clipping” in the image. Clipping is where you are “whiter than white”, the pixels have maxed out and cannot get any brighter. This allows you to see where you are sacrificing detail because of the adjustments you are making. To get the clipping display, hold the Alt key whilst moving the exposure and shadow sliders.

Saturation control
As with the saturation control in your normal image editing program, the saturation control the saturation of colours in the image. Personally I never touch this control in ACR, I prefer to adjust the saturation in Photoshop, you can tweak if you wish.

Output the image
At the bottom of the ACR box, there are settings used to change the way that your raw image is to be output. The Depth drop-down box allows you to choose either 8 Bits/Channel or 16 Bits/Channel. 16 Bits/Channel provides the maximum amount of information in the final file. Immediately converting the image to 8-bit at this stage will remove much of the benefit of capturing in RAW mode to begin with. You may have to convert to 8-bit depth later on if you take your prints elsewhere to get them printed as some machines are not setup to read the 16-bit file formats.

Having output the image from your raw processing tool you will then have an image in a file format that can (hopefully) be read by a standard image editing application. Your raw processing will have hopefully done a lot of the work that you would otherwise have done on a JPEG file when using that capture mode on the camera. There is nothing to stop you carrying on and editing the image using your standard package once you’ve got this far.

Other settings
There are plenty of other settings that can be tweaked in ACR, and no doubt in other raw processing tools too. The purpose of this article is to get people up to speed on the basics of raw processing, not an exhaustive tutorial. If anyone wishes to put together an “Advanced Raw Processing” tutorial then please feel free to contribute by starting a new thread.

I hope this is of help to someone.

Regards,

Duncan.

[Craftysnapper]

I read this article too ..and although I do shoot in Raw quite a bit I'm never happy with putting everything in inflexible boxes
Now if I tell you that all the images for the latest Pirelli calender were shot in high quality jpeg then converted to B&W, then it would seem one top pro does not follow the photographic magazine mantra

[yelvertoft]

I put together the tutorial to try and give some basic guidance to WPF members that may have felt intimidated by the idea of using raw. Personally I use jpeg for about 99% of all my pictures.

It comes as no surprise that pro's are using jpeg. If anything, they are much more likely to "get it right" to begin with and thus not need to twiddle the raw file to beat it into shape later. I only use raw if I think it's going to be a really oddball exposure, the raw file gives me a bit more flexibility to correct it later.

[Gidders]

Excelent RAW Primer Duncan.

I would agree that if you have got the lenses (cash) so that you don't need to crop significantly, and if you can guarantee the exposure then shooting in RAW doesn't give much advantage over high quality .jpp. That said on my camera (Minolta A2) HQ jpgs come out at ~8Mb v RAW ant 10Mb so the space saving on a card in not great.

In his book Real World Camera Raw, Bruce Frazer advocates over exposing for the highlights (very slightly - ~1/4 - 1/2 stop) which is contrary to conventional digital exposure wisdom, and then bringing the highlight detail back in your converter as a way of enhancing shadow detail.

Any post processing treatment distroys pixel values. Therefore the more that you start with the less image degredation. One of the benefits of RAW is that one can convert to 16 bit images rather than 8 bit so even the basic act of applying levels will result in less noise etc.

As Duncan says, a lot depends on the final output medium - if its 800 x 600 for web viewing the difference is probably indetectable, but at prints of A4 its a different matter. If the Pirelli calender boys (or girls) are converting to B&W then they are throwing away a lot of their captured data anyway so there is probably no point in them shooting in Raw.

I use ARC via bridge and the small post processing time penalty is worth it for the flexibility (to me at least)

[mcapper]

Excellent thread and much appreciated having just taken my first RAW photos at the weekend and downloaded RAW Shooter Essentials. I've printed this thread out and will use it a lot I think.

I have to say, being able to process the image and then produce a high quality tiff file is appealing but I did find the whole process very slow and tedious and the resultant tiff files take an age to load up. I also found the resultant tiff slightly softer than I thought it would be. Is this the software? I have the Canon 350D (Christmas present!) and kit lens which I've heard is a bit soft. Could it be that?

I'm starting to think that more often than not I will use high quality jpeg.

I have also got Photoshop 7 but not yet loaded it onto the computer. I've got the basic photoshop elements already on there. Is there much point to loading photoshop 7.0? Will it do lots more? And, when I do shoot in RAW, will it help with processing these files if I continue to use Raw Shooter Essentials for the conversion?

I don't know why, but I am slightly hesitant about loading photoshop 7.0 now I am used to Photoshop elements.

Any opinions gratefully received.

Many thanks

Matthew

[kennygee]

I don't think it is a problem to have both versions installed at the same time. This gives you the opportunity to try the later version and delete if you don't like it.

You could keep PS7 installed until you discover a situation that may require further facilities than Elements - using Elements for doing the basics as you do at present.

I did this when upgrading from Elements 2 to 3.

[Gidders]

Originally Posted by mcapper

I also found the resultant tiff slightly softer than I thought it would be. Is this the software? I have the Canon 350D (Christmas present!) and kit lens which I've heard is a bit soft. Could it be that?

I don't know about the 350D kit lens, although if you do not get the same problem shooting in jpg then that’s not the answer.

The other alternative is that the camera inbuilt algorithm for converting RAW to jpg will (usually) apply some sharpening, where as your RAW conversion software may not do so (automatically).

Adobe Camera RAW gives the option to set the amount of sharpening (and noise reduction) applied by the RAW conversion from nil to 100 (arbitrary units). I was taught to do noise removal as the first post processing process, and sharpening as the last. Therefore I have a level of noise removal set (dependant on the ISO I shot at) to be done by default when I convert, but no sharpening. When I have finished any retouching, I then apply sharpening in PS using Smart Sharpen before printing.

So it could be your tiff file just needs some modest sharpening applying – try unsharp mask or smart sharpen set somewhere between 75%-150% with the pixel radius set 0.5 – 1.0 pixels keeping the threshold at 0

[Nigel G]

I would agree with Gidders advice on sharpening. I used RSE and now Rawshooter Premium which has more flexibility on sharpening but still get a better JPEG result sharpening in Photoshop. (Elements2.0 in my case).

[mcapper]

Many thanks for the advice which I have put into action

Matthew

[yelvertoft]

Having said that I rarely use raw capture, there are times when it is worthwhile. I recently visited Ely cathedral, without a tripod. The roof is a long way up and it's pretty dark up there on a dull day in Feb. I attach a crop of the picture taken in jpeg mode.


The same settings, using raw capture and Adobe Camera Raw to process, you get this:
http://www.worldphotographyforum.com...=500&ppuser=34

I was quite surprised by the difference. I'll still only use it when I think it's really neccessary but bear in mind that it's there when you need it.

Duncan.